These theories naturally arise as the world volume theories on a stack of \(N\)  parallel D3 branes probing an F-theory singularity of \((I^\ast _0, D_4)\)  type — i.e., an \(\mathrm {O7}^-\)  plane coinciding with four \(\mathrm {D7}\)  branes [1]}, [2]}, [3]}, [4]}. But it is not known how to turn on the antisymmetric mass \(M\)  deformation in the F-theory construction.
